I have seen the following sentence on a news web site, which was telling about a volcano eruption. A sentence including "a good" surprised me, as I have not seen it used like this. Here is the sentence:
"...You could hear and feel the eruption a good half a mile away, and the closer you got, the more you could feel it..."
What does "a good" mean here? Does it mean "they could hear it well" or does it mean "they could hear it from a distance which was as far as a mile long".